Cerebrovascular deposition of the amyloid beta-protein (AB), a condition known as cerebral amyloid angiopathy (CAA), is a common pathological feature of patients with Alzheimer's disease (AD) and related disorders and is a primary cause of cerebral hemorrhage. The reason as to why cerebrovascular AB deposition leads to loss of vessel wall integrity and hemorrhagic stroke in CAA remains unresolved. AB is proteolytically derived from its parent molecule the amyloid beta-protein precursor (ABPP), which possesses potent anticoagulant properties. ABPP and its derived fragment AB are intimately involved in the pathology of CAA. A major thrust in our laboratory is to understand how ABPP and AB contribute to this vessel wall pathology, including cerebrovascular cell death, loss of vessel wall integrity, and cerebral hemorrhage. In this regard, we have focused on developing invaluable in vitro and in vivo models of CAA involving ABPP and AB. Recent findings from our laboratory have implicated ABPP, urokinase-type plasminogen activator (uPA) and members of the matrix metalloproteinase (MMP) family as potential contributors to these pathologic events in CAA. In light of these recent findings, the hypothesis that forms the basis of this proposal is that cerebrovascular deposition of AB enhances the expression and accumulation of factors that alter the local proteolytic environment of the cerebral vessel wall contributing to cerebrovascular cell degeneration, loss of vessel wall integrity and cerebral hemorrhage. The broad objectives of this proposal are two-fold. First, our major emphasis will be to investigate downstream alterations in proteolytic mechanisms that can be influenced by AB deposition and/or ABPP accumulation that may contribute to the pathology of CAA. Second, we will determine if alterations in these proteolytic systems can influence cerebrovascular AB deposition. The planned experiments are multi-tiered and will take advantage of unique cerebrovascular cell culture systems for in vitro studies and novel transgenic mice for in vivo studies modeling CAA. Specifically, the aims of this proposal are to 1) determine if over expression of ABPP on the surfaces of cultured human cerebrovascular cells influences AB deposition and hemostatic reactions; 2) investigate the expression, activity, and consequences of uPA in in vitro and in vivo models of CAA.and 3) investigate the expression, activity, and consequences of specific matrix metallo-proteinases (MMPs) in in vitro and in vivo models of CAA. Completion of these studies will provide new important mechanistic information about pathological functions of AB and ABPP and how they can modulate local proteolytic mechanisms that occur in the cerebral vessel wall in CAA influencing AB deposition and/or loss of vessel wall integrity. The information generated from our proposed studies may provide new insight into the development of therapeutic strategies to mitigate both cerebrovascular AB deposition and the subsequent pathological consequence of hemorrhagic stroke in CAA. [unreadable] [unreadable]